1. Field of the Invention
The present invention concerns a local coil arrangement for magnetic resonance applications, of the type wherein the local coil arrangement has a support structure in which the antenna arrangement is embedded, and the antenna arrangement has a number of magnetic resonance antennas, wherein a magnetic resonance excitation signal can respectively be emitted by means of each magnetic resonance antenna and/or a magnetic resonance signal can respectively be received by means of each magnetic resonance antenna.
The present invention furthermore concerns a magnetic resonance system of the type having a basic that generates a static basic magnetic field with a field strength that is spatially homogeneous within an examination region of the magnetic resonance system and that is greater than a minimum field strength, at least one local coil arrangement of the type described above that can be introduced into and removed from the examination region, and a control and/or evaluation device that, in terms of signaling, can be connected at least temporarily with the antenna arrangement of the local coil arrangement to emit magnetic resonance excitation signals and/or to receive magnetic resonance signals.
2. Description of the Prior Art
Local coil arrangements are used in order to excite magnetic resonances only locally and/or in order to detect previously excited magnetic resonance signals only locally but with better signal-to-noise ratio.
For use, the local coil arrangement is applied on an examination subject (often a person). The examination subject is hereby normally located on a patient bed. The local coil arrangement can alternatively be attached directly to the patient bed or to the examination subject. After the application of the local coil arrangement, the patient bed (including the examination subject located thereon and including the local coil arrangement) is introduced into the examination region of the magnetic resonance system, the desired examination is conducted and then the patient bed is brought out of the examination region again.
When they should emit a magnetic resonance signal or should receive a magnetic resonance signal, the magnetic resonance antennas of the local coil arrangement must be resonant at the Larmor frequency of the magnetic resonance system. Due to the fact that the travel range of the patient bed is normally greater than the length of the examination region of the magnetic resonance system, however, the operation the local coil arrangement is only reasonable when the local coil arrangement is located in the examination region. When the local coil arrangement is located outside of the examination region, the magnetic resonance antennas of the local coil arrangement would even have a disruptive effect. For this reason, the magnetic resonance antennas of the local coil arrangement are only activated when the local coil arrangement is located in the examination region. Otherwise they are deactivated. The activation and deactivation hereby ensues via corresponding activation of detuning circuits that are associated with the magnetic resonance antennas.
An additional problem in local coil arrangements is the number of signal channels required. Often many local coil arrangements are present, wherein only a portion of the local coil arrangements are located in the examination region at any point in time, however. Via time-accurate connection of the respective magnetic resonance antennas with the control and/or evaluation device, the number of the required transmission channels can be distinctly reduced.
Various procedures are known in the prior art for time-accurate tuning/detuning and for time-accurate connection with the control and/or evaluation device. For example, it is known to determine the positions of the local coil arrangements with the aid of magnetic resonance imaging. In this case a separate adjustment step is necessary for the position detection. After the adjustment, the corresponding local coil arrangements are wired and selected in a complicated matrix.